large scale Baird/Nipkow Televisor project "Big Paul"

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large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Sun Mar 05, 2017 10:20 pm

Dear NBTV forum members,

Let me introduce myself first: I am an artist in the field of media technology, based in Vienna, Austria. In the last years, I completed a series of "media archaeological" art installations related to the history of television. Here are three examples of my work:
- "VinylVideo™" is a system that allows storage and playback of an analog video signal via a standard 12" 45rpm vinyl audio record, using a regular turntable and TV set http://gebseng.com/03_vinylvideo/.
- "VSSTV" (Very Slow Scan Television) receives SSTV signals sent by HAM radio amateurs and then "prints" them by filling up bubble wrap with coloured ink http://gebseng.com/02_vsstv/.
- "A Parallel Image" tries to build a non-sequential method of transmitting moving images with electricity, using a lot of cables and light bulbs http://gebseng.com/08_a_parallel_image/.

At the moment, I am working on a new project in this field, "Big Paul", which tries to build a large scale Baird/Nipkow Televisor with a resolution of 240 lines. For funding and sponsoring purposes, I put together a brochure, which you can find here: http://gebseng.com/11_big_paul/big_paul_brochure.pdf.

In this thread, I want to share my research efforts so far, it would be great to get comments from you all!

best,

Gebhard
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby Andrew Davie » Sun Mar 05, 2017 11:12 pm

gebseng wrote:I want to share my research efforts so far, it would be great to get comments from you all!
''

Welcome! I love your projects. The Vinyl TV I recall seeing quite a long time ago - I want one!
Good luck with your project - although our forum doesn't have a lot of active members, we do have some extremely skilled people who will no doubt lend their expertise as required.
Feel free to use the forum for posting videos/images and updates as you see fit.
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Sun Mar 05, 2017 11:16 pm

Thanks Andrew, I appreciate it!
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Mon Mar 06, 2017 8:48 pm

Dear forum members,

Since I did not find a software that allowed me to design a Nipkow disk with the parameters I need, I started doing my own calculations, which you can find here:

vertical scanning disk (image will be viewed on right side, scan lines appear vertical) with 240 holes

disk diameter: 1,490 mm
disk circumference: 4,680.973 mm
outermost hole: 50 mm from disk edge, radius 695 mm, circumference 4,366.814 mm
innermost hole: radius 640.508 mm, circumference 4,024.430 mm
image height at outermost hole (4,366.814 / 240) = 18.195 mm
(image height at innermost hole (4,024.430 / 240) = 16.768 mm)
image width = 54.492 mm
aspect ratio appr. 1:3
hole size: (54.492 / 240) = 0.227 mm

do my assumptions sound about right to you?

I attached a design as .png and autocad .dxf

best,

geb

nipkow disk 1490mm 240 lines mit rand.png
(7.38 MiB) Not downloaded yet


nipkow disk 1490mm 240 lines mit rand.dxf
(182.08 KiB) Downloaded 163 times
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby Andrew Davie » Mon Mar 06, 2017 10:35 pm

gebseng wrote:Since I did not find a software that allowed me to design a Nipkow disk with the parameters I need, I started doing my own calculations, which you can find here:


There are standards (32 lines springs to mind) which would make your life easier. More particularly, there's software that converts from video format into those standards. I'm not sure 240 lines is a standard, but in any case the software I'm referencing is "Video2NBTV" by Gary. It would make your life easier to consider these pre-existing formats. You also have chosen a completely different aspect ratio to the standards I know. So again - why be different?

I was looking at the size of your disc (!) and thinking "gosh, that's going to be dangerous!" - you haven't mentioned a frame rate. Although you've massively increased the scanlines over a "standard" NBTVA format (which is 32 lines), you're actually displaying a tiny image. 32 scanlines gives suprisingly good pictures, done right. Anyway, frame rate will determine how fast the disc has to spin (currently 12.5Hz = 750rpm). I've done lots of playing by using an audio editor to "speed up" some of the videos I play, and to some degree they look "better" because they're (slightly) less flickery, but ultimately you're affected by the amount of light that gets through any hole. If you're increasing the scanlines then you're decreasing the hole diameter (for a given disc size) so that's a consideration - are your holes big enough to allow sufficient light through. You may have to consider an incredibly bright lights source. Let's assume you are going with the 12Hz frame rate, then you have your outer edge travelling 4,680.973 mm (circumerence) * 12.5 (frame rate) mm/s = I make that 58 m/s. I don't do 3-digit precision so to the meter is close enough :). That's hefty, and probably dangerous. I am unsure if you will have issues, but I expect a huge motor will be required! I would assume if the motor isn't noisy, the spinning disk probably will be!

I suggest you slightly enlarge your holes (just a fraction) to give a bit of overlap between them - and consider the shape. Round holes, diamond holes, square holes - they all have characteristics which affect the picture.

Now a general comment - I understand you're exploring technology and alternate ways of showing images, particularly related to TV. One alternate that I haven't seen anywhere is to place the holes on a very long looped belt and pull that through in front of the light source at high speed. You could get a much bigger picture, but with a really weird mechanism. The picture would be totally rectangular rather than arced. The technological challenge is pulling a long (very) belt efficiently and somehow managing it once it's passed the viewing area. If the image was (say) 10cm high, and we had 32 scanlines, then the belt would be 320cm long. That seems manageable and already you have an image that's way bigger than any Nipkow disk. You'd have to pull it through at 10*32*12.5 cm/s which is 40m/s and although do-able, quite the technical challenge I think. Anyway, just throwing that one out there.

Back to your concept - in summary
* wow, that's a big disk
* holes may be too small at 240 line resolution to actually see an image?
* format you choose is non-standard, requiring lots more work to create content
* picture is tiny!
* frame rate is undefined, but affects heavily the practicality of using that big disk.
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby Klaas Robers » Tue Mar 07, 2017 7:32 am

When you go to higher line counts, the untransparency of the disc grows quadratic. For just 32 lines the disc is for 99.9% black, you get only 0.1% of the light. For 240 lines this is quadratic worse. Look:

Assume a square image, 240 x 240 pixels = 58 000 pixels. One is transparent. That is 1.7 10^-5. You will end up with a very, very dim picture, even with many ultra bright LEDs behind the disc.

It is a good plan to do things that others didn't bring to a good end, may be you are brighter. But the normal Nipkow disc looks to be unable to solve this problem.

I would advise you to start with a 32 line disc. Make it 1.5 meter large and see what you can.
Then switch to 60 or 64 lines, and solve the problems you encounter.
When you have a working system, make live again 4 times more difficult: 120 lines.

Following that road gives you experience with the growing problems and how you can solve them. And then Vic Brown has invented solutions to make larger pictures by multi spirals on the disc. But that invests in greater disc speeds and with a disc of 1.5 meter, you will find the speed of sound your limiting factor.
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Wed Mar 08, 2017 8:16 am

Hi Andrew,

Thanks a lot for your detailed post, which of course gives me a lot to think about!

Andrew Davie wrote:
There are standards (32 lines springs to mind) which would make your life easier. More particularly, there's software that converts from video format into those standards. I'm not sure 240 lines is a standard, but in any case the software I'm referencing is "Video2NBTV" by Gary. It would make your life easier to consider these pre-existing formats. You also have chosen a completely different aspect ratio to the standards I know. So again - why be different?


I am well aware of existing standards in the mechanical TV community. A couple of years ago, my students and me built a 32 line Baird Televisor from scratch in a four day workshop, and we used "Video2NBTV" for encoding. For this project, however, I might not need an encoder at all, since I plan to build not only the receiver, but also the camera to have live transmissions from one rotating disk to the other.

I was looking at the size of your disc (!) and thinking "gosh, that's going to be dangerous!" - you haven't mentioned a frame rate. Although you've massively increased the scanlines over a "standard" NBTVA format (which is 32 lines), you're actually displaying a tiny image. 32 scanlines gives suprisingly good pictures, done right. Anyway, frame rate will determine how fast the disc has to spin (currently 12.5Hz = 750rpm). I've done lots of playing by using an audio editor to "speed up" some of the videos I play, and to some degree they look "better" because they're (slightly) less flickery, but ultimately you're affected by the amount of light that gets through any hole.
If you're increasing the scanlines then you're decreasing the hole diameter (for a given disc size) so that's a consideration - are your holes big enough to allow sufficient light through. You may have to consider an incredibly bright lights source. Let's assume you are going with the 12Hz frame rate, then you have your outer edge travelling 4,680.973 mm (circumerence) * 12.5 (frame rate) mm/s = I make that 58 m/s. I don't do 3-digit precision so to the meter is close enough :). That's hefty, and probably dangerous. I am unsure if you will have issues, but I expect a huge motor will be required!


Yes, very dangerous indeed! I calculated the rim speed for the 1500mm disk at 253 km/h (157 mph) (900 rpm for 15 fr/sec). this is about the same speed as a 12,000 rpm angle grinder with a 125mm disk....
But of course I will take all the necessary precautions and build a solid case around the Nipkow disk. I am already collaborating with a mechanical engineer to make sure we choose the right materials and technology for achieving this safely.
About the scan lines: increasing the number from 32 up to something around 200 kind of is the point of my whole endeavour, since I want to create a mechanical TV system that (at least in theory) could have existed in the 1950s or '60s. And the fact I really like about the whole Nipkow principle is that you can only increase resolution by making the disk much bigger!
I am also working with an electrical engineer for motor control, we are currently considering a 1.5 kW motor, that would still need about a minute to bring the disk up to speed.
The remaining brightness with 0.25mm holes is of course to be considered, I'll try to calculate that.

I would assume if the motor isn't noisy, the spinning disk probably will be!


I'm afraid so.I read that 240 frames at 900 rpm will give you a siren effect with a 3,600 Hz sound. Do you think that the small size of the holes will keep the volume tolerable?

I suggest you slightly enlarge your holes (just a fraction) to give a bit of overlap between them - and consider the shape. Round holes, diamond holes, square holes - they all have characteristics which affect the picture.


I'll have to see if a different shape than round can be achieved with these small diameters (I read that square holes would give you about 25% more brightness). Funny enough, I also considered the holes to be overlapping, would that help with the visibility of scanlines?

Now a general comment - I understand you're exploring technology and alternate ways of showing images, particularly related to TV. One alternate that I haven't seen anywhere is to place the holes on a very long looped belt and pull that through in front of the light source at high speed. You could get a much bigger picture, but with a really weird mechanism. The picture would be totally rectangular rather than arced. The technological challenge is pulling a long (very) belt efficiently and somehow managing it once it's passed the viewing area. If the image was (say) 10cm high, and we had 32 scanlines, then the belt would be 320cm long. That seems manageable and already you have an image that's way bigger than any Nipkow disk. You'd have to pull it through at 10*32*12.5 cm/s which is 40m/s and although do-able, quite the technical challenge I think. Anyway, just throwing that one out there.


Great idea! I also read about the belt concept. It reminds me a little bit of the Tefifon, an obscure audio tape format from the '50s that used a plastic strip with a mechanical groove instead of magnetic tape, kind of like a vinyl record morphed into an audio cassette (https://en.wikipedia.org/wiki/Tefifon)
With this project however, I really want to stick with the Nipkow Disk, because I really like the simplicity and technical transparency of this historically very first idea of how to break up a moving image into lines and frames.

Back to your concept - in summary
* wow, that's a big disk
* holes may be too small at 240 line resolution to actually see an image?
* format you choose is non-standard, requiring lots more work to create content
* picture is tiny!
* frame rate is undefined, but affects heavily the practicality of using that big disk.


Thanks for summarizing your concerns, all of them valid of course. As mentioned above, having a huge disk with a tiny but very high resolution image is kind of the raison d'être for the whole project (stupid, I know).

best,

geb
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Wed Mar 08, 2017 8:38 am

Klaas Robers wrote:When you go to higher line counts, the untransparency of the disc grows quadratic. For just 32 lines the disc is for 99.9% black, you get only 0.1% of the light. For 240 lines this is quadratic worse. Look:

Assume a square image, 240 x 240 pixels = 58 000 pixels. One is transparent. That is 1.7 10^-5. You will end up with a very, very dim picture, even with many ultra bright LEDs behind the disc.

It is a good plan to do things that others didn't bring to a good end, may be you are brighter. But the normal Nipkow disc looks to be unable to solve this problem.

I would advise you to start with a 32 line disc. Make it 1.5 meter large and see what you can.
Then switch to 60 or 64 lines, and solve the problems you encounter.
When you have a working system, make live again 4 times more difficult: 120 lines.

Following that road gives you experience with the growing problems and how you can solve them.

Hi Klaas,

Thanks for the valuable information! The brightness looks like a serious problem indeed, and thank you for summing up the math behind it. Starting with a large disk with fewer/larger scan lines is a reasonable suggestion of course. I might not be able to do that, since precision CNC manufacturing these large disk will be pretty expensive. But I could start with building a smaller (say, 12") Nipkow disk with 0.25 mm holes. Do you think that would help me to assess the achievable brightness?

And then Vic Brown has invented solutions to make larger pictures by multi spirals on the disc. But that invests in greater disc speeds and with a disc of 1.5 meter, you will find the speed of sound your limiting factor.


Yes, I also read about this idea. But, as you point out yourself, going from 900 to 2700 rpm is not something I think is achievable for me.

best,

geb
Last edited by gebseng on Fri Mar 10, 2017 6:55 am, edited 1 time in total.
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Wed Mar 08, 2017 8:45 am

For fun, I tried to calculate Nipkow disk diameters and rim speeds for contemporary video resolutions:

PAL (768 vertical lines, 25 fr/sec, 14” screen (4:3) = 285 x 213 mm):
1.500 rpm
768 scan holes
hole diameter 0.37 mm
disk circumference 164 meters
disk diameter 52 meters
rim speed 8,900 km/h

Full HD (1920 vertical lines, 60 fr/sec, 40” screen (16:9) = 886 x 498 mm):
3,600 rpm
1,920 scan holes
hole diameter 0,5 mm
disk circumference 956 meters
disk diameter 304 meters
rim speed 206.531 km/h (0,02% speed of light, mach 169?)

can the more mathematically inclined among us corroborate these numbers?

best,

geb
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gary » Wed Mar 08, 2017 9:45 am

NipkowDXF has an inbuilt calculator that you can use to verify your calcs:
http://users.tpg.com.au/users/gmillard/ ... Nipkow.zip

Just go to "disk/Create Disk" enter your required parameters and press calc next to "aperture step".

"aperture step" is, of course, the optimum width of the aperture, it is quite common to increase this size to provide some overlap to reduce line structure, hence it is referred to as "aperture step" rather than "aperture size".

In addition, by convention, we assume the aspect ratio to be at the mid point of the aperture area so there may be a slight variation to your own calculation depending on where you have taken that value to be.
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby Andrew Davie » Wed Mar 08, 2017 4:38 pm

I haven't checked all of your figures, but just wanted to talk about your use of comma separators and/or dot separators and/or no separator.
It's a bit confusing! You use "1.500" and "8,900" and "206.531"; it's pretty important to be consistent because the first I believe you are saying "1500", the second "8900" and the third "206531". Just thought I'd note that.

I'll try out the second one (HD) without digit separators to remove any ambiguity in my answer.
Speed of light: 299792458 m/s

Disk diameter 304 m that gives circumference of closer to ~955 m. (Pi * 304)
Each revolution: 955 m.
Rotating 60 f/s = 57300 m/s

57300 / 299792458 = 0.00019113222655 fraction of light speed
*100 (to %) = 0.019 % percentage of light speed CONFIRMED

speed of sound ~= 340 m/s

mach number = 57300/340
= 168.5 CONFIRMED

Looks good to me :)


Gan't wait for Geb's Relativistic Effect Televisor :)




gebseng wrote:For fun, I tried to calculate Nipkow disk diameters and rim speeds for contemporary video resolutions:

PAL (768 vertical lines, 25 fr/sec, 14” screen (4:3) = 285 x 213 mm):
1.500 rpm
768 scan holes
hole diameter 0.37 mm
disk circumference 164 meters
disk diameter 52 meters
rim speed 8,900 km/h

Full HD (1920 vertical lines, 60 fr/sec, 40” screen (16:9) = 886 x 498 mm):
3,600 rpm
1,920 scan holes
hole diameter 0,5 mm
disk circumference 956 meters
disk diameter 304 meters
rim speed 206.531 km/h (0,02% speed of light, mach 169?)

can the more mathematically inclined among us corroborate these numbers?

best,

geb
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby Klaas Robers » Wed Mar 08, 2017 6:34 pm

Any way consider to run the disc in a vacuum chamber (a 1.6 meter sphere, with a small flat area where the viewing window is. That will limit the needed power very much, and the noise the disc will be making with these speeds. Have you already made a estimation of the amount of sound? When you need a 1.5 kW motor, I assume almost all that power is going to be sound?
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Fri Mar 10, 2017 6:53 am

gary wrote:NipkowDXF has an inbuilt calculator that you can use to verify your calcs:
http://users.tpg.com.au/users/gmillard/ ... Nipkow.zip

Just go to "disk/Create Disk" enter your required parameters and press calc next to "aperture step".

"aperture step" is, of course, the optimum width of the aperture, it is quite common to increase this size to provide some overlap to reduce line structure, hence it is referred to as "aperture step" rather than "aperture size".

In addition, by convention, we assume the aspect ratio to be at the mid point of the aperture area so there may be a slight variation to your own calculation depending on where you have taken that value to be.


Hi Gary,

Thanks for your post!

I already tried your great Nipkow Disc DXF Generator about a week ago, but stumbled over the 128 lines limit. Now I tried it again, and I see that you changed that, thank you so much! I was already thinking about contacting you about that, but was afraid it would be too much of a hassle.

I have some questions regarding your software:
- DXFNipkow.exe generates a .DXF file. I tried to import it to Autodesk Fusion 360, where I successfully imported other .DXF files before. However, with the NipkowDXF.dxf, I got an error message and could not open it. Do you have any idea what the problem could be? (I am not an engineer and don't have easy access to other CAD software)
- I assume, when choosing "Metric" as Drawing Unit, that means millimetres?
- What are the differences between "Create Disk", "Create Hub" and "Create Encoder"?

Again, thank you so much, this is really useful for me.

best,

geb
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Fri Mar 10, 2017 7:05 am

Hi Andrew,

Andrew Davie wrote:I haven't checked all of your figures, but just wanted to talk about your use of comma separators and/or dot separators and/or no separator.
It's a bit confusing! You use "1.500" and "8,900" and "206.531"; it's pretty important to be consistent because the first I believe you are saying "1500", the second "8900" and the third "206531". Just thought I'd note that.


Very sorry about that. That comes from translation from German to English. In the future, I will use no thousands separator, and a dot as a decimal separator. (In German, it is a comma for decimals and a dot for thousands, plus the million/milliard thing instead of million/billion, really confusing).


mach number = 57300/340
= 168.5 CONFIRMED

Looks good to me :)


Good to hear that, thanks!


Gan't wait for Geb's Relativistic Effect Televisor :)


Don't hold your breath, this will take some time. But I'll keep you updated in this thread.
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Re: large scale Baird/Nipkow Televisor project "Big Paul"

Postby gebseng » Fri Mar 10, 2017 7:11 am

Klaas Robers wrote:Any way consider to run the disc in a vacuum chamber (a 1.6 meter sphere, with a small flat area where the viewing window is. That will limit the needed power very much, and the noise the disc will be making with these speeds. Have you already made a estimation of the amount of sound? When you need a 1.5 kW motor, I assume almost all that power is going to be sound?


Hi Klaas,

I'm afraid the vacuum chamber would be a bit too much construction wise :?
I was not able to make calculations regarding the sound level, since I lack the knowledge to do that. I only assume the frequency to be 3600 Hz (240 * 15), but other than that I'm pretty clueless so far. I hope that the small diameter of the apertures (0.5 mm or less) will be enough to keep the volume low.

best,

geb
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